Developing a Java Applet to restrict access to a particular directory tree

I am creating a Java based applet to secure a file system directory(Directory here stands for开发者_StackOverflow中文版 the folders) tree from being accessed directly. So that user can only use the files if he accesses them through the applet. For this I think to implement X.500 along with profiles of the user and using X.509 certificates to check their credentials. But I am not able to think how to make all this available through Java applet. Any help will be apreciated

Why? You don't say which LDAP implementation you are using, but certainly OpenLDAP can do that automatically based on the user identity. You don't need to write an applet for that, or at least if you do all you need is to give it a more privileged userID to log in with than users generally get access to.